Screen cleaning device

ABSTRACT

Apparatus for maintaining a vehicle screen ( 12 ) supported with respect to a vehicle by a gasket ( 16, 24 ), said screen ( 12 ) comprising first ( 22 ) and second ( 27 ) edge regions wherein said gasket ( 16, 24 ) has a first conduit ( 20 ) means having an opening ( 21 ) proximate to said first edge region ( 22 ) and second conduit ( 25 ) means having an opening ( 26 ) proximate to said second edge region ( 27 ) and wherein the apparatus further comprises supply apparatus coupled to said first conduit means ( 20 ) for supplying a liquid thereto and collection apparatus coupled to said second conduit ( 25 ) means for collecting said liquid.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for maintaininga vehicle screen such as for example a vehicle headlamp.

2. Description of the Related Art

Vehicle screens such as headlamp lenses and windscreens require cleaningin order to retain their translucent properties. As dirt is depositedand collects on the surface of the screen the amount of light passingthrough the screen is diminished. In the case of a windscreen thisreduces visibility. In headlamp applications deposited dirt on the lenscan form a reflective layer as well as reducing light output. Light cantherefore be reflected back towards the reflector and out of theheadlamp in undetermined directions thereby causing glare. This problemis exacerbated by the heating effect caused by the light beam. As liquidcontacts the headlamp lens, the beam tends to heat and thereby evaporatethe liquid leaving any dirt previously suspended in the liquid on thesurface of the headlamp. This so-called “burn-on” effect can increasethe glare from a headlamp substantially.

Numerous techniques have been suggested in the past for overcoming theseproblems. Some of these solutions have used wipers to remove the dirtoften requiring some form of water nozzle to spray water or cleaningliquid onto the screen surface prior to wiper action.

Problems are associated with many of these solutions. For example, theyare prone to mechanical failure of the wiper components and to acleaning liquid reservoir becoming empty since the liquid is notrecycled but is lost as soon as it is sprayed. Furthermore, the driveris usually required to take positive action to clean the screen.

It is therefore an object of the present invention to at least partlymitigate the difficulties of the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided amethod of maintaining a surface of a translucent screen of a vehiclecomprising the steps of providing a first edge region of said screensurface with liquid, causing the liquid to flow across the surface fromthe first edge region in the direction of a second edge region, andcollecting said liquid in said second edge region, whereby said firstedge region is selected from a top edge region and a bottom edge region,located below said top edge region, in response to said detected vehiclevelocity.

According to a second aspect of the present invention there is providedapparatus for maintaining a vehicle screen supported with respect to astructure by a gasket, said screen having a first and second edgeregion, said gasket having first conduit means having an openingproximate to said first edge region and second conduit means having anopening proximate to said second edge region, wherein said structure isa vehicle and said screen is a headlamp screen and said first edgeregion is disposed below said second edge region, and wherein the systemfurther comprises supply apparatus connectable to said first conduitmeans for supplying a liquid thereto and collection apparatusconnectable to said second conduit means for collecting said liquid.

DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

An embodiment of the present invention will now be described hereinafterby way of example only with reference to the accompanying drawings inwhich:

FIG. 1 shows a cross-section to a vehicle headlamp for use in accordancewith the present invention.

FIG. 2 shows a schematic layout including the vehicle head lamp andscreen maintenance apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the Figures, like reference numerals refer to like parts.

Referring now to FIG. 1, a headlamp 10 comprises a translucent screen12, hereinafter referred to as a lens having an upper edge region 22 anda lower edge region 27, a body portion 11 and gasket portions 16, 24.The lens is secured around its periphery to the body portion 11 via thegasket portions. In the preferred embodiment the gasket may be formed bya tubular elastomeric moulding. The lens is of plastics, egpolycarbonate and has a generally convex cross-section. The upper edgeregion is disposed rearwardly of the lower edge region, to the left asseen in the Figure. The lower edge region is thus below the upper edgeregion.

The headlamp housing is secured to a first lower vehicle panel 14, and asecond upper vehicle panel 15 to which are fixed the gasket portions 24,16 respectively surrounding the headlamp lens 12.

A light bulb and reflector (not shown) are supported in the body portion11 in a conventional manner to provide a beam of light from theheadlamp.

A first vehicle panel 14 is generally disposed below the lower edgeregion 27 of the lens 12 and extends generally forward of the lens. Asecond vehicle panel 15 is disposed generally above the upper edgeregion 22 of the lens and extends generally rearwardly of the lens. Thesecond panel 15 has a generally convex region proximate the lens 12 soas to provide a generally air-smoothed form. The shape of the panel 14,lens 12 and panel 15 is such that as the vehicle moves forward in thedirection of the arrow 18, air flowing across the front of the vehicleflows generally upwardly across the outer surface of the lens 12 in thedirection shown by the small arrows shown in FIG. 1.

The portion 16 of the gasket to which is secured the upper edge of thelens 12 has a first conduit 20 running through it. A liquid may flowalong the conduit, as will be described herein below. A first duct 21leads from the first conduit 20 through the gasket wall to a region 22at the top edge of the lens.

Likewise the portion 24 of the gasket which is secured to the lower edgeof the lens has a second conduit 25 running through it along which aliquid can flow. A second duct 26 leads from the second conduit 25 to aregion 27 at the bottom edge of the lens.

FIG. 2 shows liquid supply apparatus 30 which includes a first andsecond connecting pipe 31, 32, a filter portion 34, a liquid source 35(for example a self-wetting formulation) and a pump 36. The firstconnecting pipe 31 is connected to the first conduit 20 to allow liquidto flow through the pipe 31 into first conduit 20. The connecting pipe32 is connected to the second conduit 25. The two connecting pipes 32,31 are also connected to liquid control apparatus 33.

The liquid control apparatus 33 includes the filter portion 34, liquidsource 35 and the pump 36. The filter portion 34 is connected to theother end of each of the connecting pipes 31, 32. Liquid 35 is stored ina container (not shown) to provide. a source of the liquid. The liquidis pumped to and from the container along the connecting pipes 31, 32 bya pump 36.

Liquid control apparatus 30 is connected to receive control signals fromcontrol circuitry 37 along control signal line 38. The control circuitry37 is connected to vehicle sensor apparatus 40. The vehicle sensorapparatus includes a velocity sensor 41 for detecting the vehiclevelocity and a headlamp condition sensor 42 for controlling cleaning ofthe headlamp. The headlamp condition sensor 42 may be any type of sensorcapable of detecting the quantity of dirt or contaminant on the surfaceof the screen. For example such a sensor may be a surface resistivitysensor or a temperature detector or a scattered light detector.

The headlamp condition sensor 42 is connected to control circuitry 37 bya first signal line 43. The sensor outputs a condition control signal Con signal line 43 which is input to the control circuitry 37 forcontrolling liquid supply to the screen. The vehicle velocity sensor 41is connected to the control circuitry 37 by a second signal line 44 andoutputs a signal V_(VEH) on said signal line 44 indicating the detectedvelocity of the vehicle.

In response to the signals from the velocity sensor 41 and headlampcondition sensor 42 the control circuitry 37 outputs a control signal Pon control signal line 38 which controls operation of the liquid supplyapparatus 30. The condition control signal C causes the controlcircuitry to supply liquid to the screen whilst the vehicle velocitysignal V_(VEH) selects the mode in which liquid is supplied.

When liquid supply is initiated the cleaning apparatus can operate intwo modes as will be described hereinbelow.

In a first mode the vehicle velocity is below a threshold velocity andliquid flows generally downwardly across the lens surface under theforce of gravity. In this mode the control signal P from controlcircuitry 37 controls pump 36 to apply a positive pressure to supplyliquid by pumping liquid from the liquid source 35 along firstconnecting pipe 31 to the first conduit 20 in gasket portion 16. Liquidfrom the gasket flows through the first duct 21 to the upper edge region22 at the upper edge of the lens. The liquid in region 22 flowsdownwards across the lens surface under the force of gravity where it iscollected in lower edge region 27 at the lower edge of the lens. Thecollected liquid flows through the second duct 26 under negativepressure (caused by sucking) from the pump and into the second conduit25 running through the portion 24 of the gasket. The liquid flows fromthe second conduit 25 along the second connecting pipe 32 through thefilter portion 34 and returns to the liquid source 35 thereby recyclingthe liquid.

In the second mode of operation the vehicle velocity is above athreshold velocity such that the air flow shown by the small arrows inFIG. 1 across the surface of the lens is sufficient to cause liquidprovided by the second duct 26 into the lower edge region 27 to flowgenerally upwardly across the surface of the lens where it collects inupper edge region 22 at the upper edge of the lens. In this second modecontrol signal P on control signal line 38 controls the pump 36 tosupply liquid from the liquid source 35 along the second connecting pipe32 to the second conduit 25 running through the lower portion 24 of thegasket. Liquid in the gasket conduit 25 flows through second duct 26 tothe lower edge region 27 at the lower edge of the lens. The liquid inregion 27 is induced to flow upwardly by the movement of air caused bythe vehicle motion and collects in the upper edge region 22 at the upperedge of the lens. The collected liquid flows through the first duct 21into the first conduit 20 running through the gasket portion 16. Theliquid flows from the conduit 20 along the first connecting pipe 31through the filter portion 34 and returns to the liquid source 35thereby recycling the liquid.

In both the situation where fluid flows downwards under gravity andupwards as a result of air flow due to vehicle motion the result is thatthe fluid 17 spreads thinly across the part of the surface of the lenswhere cleaning is desired. The fluid is provided at one edge region ofthe screen and collected in another edge region depending upon thevelocity of the vehicle. As a result any dirt which would otherwise havesettled and accumulated on the headlamp lens thereby causing adeterioration in the translucency of the lens is instead entrained inthe fluid film flowing over the screen. The fluid, after flowing acrossthe screen, is filtered in the filtering apparatus to keep the fluidclean prior to recycling.

It will be appreciated that fluid flow is also to some extent dependenton the lens geometry and that instead of fluid flow being generallyupwardly and/or downwardly configurations of lens or the surroundingairflow inducing structure could cause liquid to flow to collectingregions in the side edges of the screen where ducts and conduits in thegasket could be provided to enable to liquid to be recycled.

In this way the present invention provides a method and apparatus forkeeping the lens or screen of a vehicle headlamp clean whilst recyclingthe cleaning fluid used, thereby reducing the maintenance required tokeep the cleaning fluid “topped-up”.

It will also be appreciated that as the liquid is recycled someregeneration of the liquid may be required to maintain the liquid at adesired composition. For example under precipitous weather conditionsthe liquid may tend to become more dilute as some water falling on thescreen may be collected with the liquid and be recycled. Likewise underhigh temperature conditions the concentration of the liquid may beaffected. In order to overcome these problems it is envisaged that anadjustable dosing tank 100 could be provided to supply doses ofconcentrate to the liquid source in order to maintain the liquid withina desired range of concentration.

Although the present invention has been described in respect of vehicleheadlamps it will be understood that the invention could be adapted toprovide cleaning for any screen where cleaning is desired for exampletrains, aircraft and the like.

It will also be understood that the invention may be adapted for use inonly one of the two described modes of operation. In applications forvehicles which are only capable of slow motion or where the vehicleconfiguration does not allow sufficient upward air flow across thescreen, the invention only operates in the first mode of operation whereliquid flows downwards across the lens due to gravity. Alternatively theinvention may operate only when the vehicle is travelling at relativelyhigh velocities when only the second mode of operation will be required.

What is claimed is:
 1. An apparatus for maintaining a vehicle screensupported with respect to a vehicle by a gasket, said screen includingfirst and second edge regions and said gasket including a first conduitmeans having an opening proximate to said first edge region and a secondconduit means having an opening proximate to said second edge region;said apparatus comprising: a liquid supply apparatus connectable to saidfirst and second conduit means for supplying a liquid thereto andcollection apparatus connectable to said first and second conduit meansfor collecting said liquid; and vehicle velocity detecting apparatusadapted to determine a velocity of said vehicle and output a vehiclevelocity signal for controlling the supply of liquid to the screen;wherein said supply apparatus is connectable to one of said first orsecond conduit means in response to said vehicle velocity signal.
 2. Anapparatus according to claim 1 wherein said supply apparatus comprises apump for applying a positive pressure to said first edge region tothereby pump fluid through said first conduit means to the first edgeregion.
 3. An apparatus according to claim 1 wherein said collectingapparatus comprises a pump for applying a negative pressure to saidsecond edge region to thereby pump fluid through said second conduitmeans from the second edge region.
 4. An apparatus according to claim 1wherein said first edge region is disposed above said second edgeregion.
 5. An apparatus according to claim 1 wherein said first edgeregion is disposed below said second edge region.
 6. An apparatusaccording to claim 1 further comprising a screen condition detectionapparatus adapted to detect a condition of said screen and including acondition control signal apparatus for providing a control signal forcontrolling a liquid supply to the screen.
 7. An apparatus according toclaim 6 wherein said screen condition detection apparatus is a sensoradapted to detect the quantity of dirt or contaminant on a surface ofsaid screen.
 8. An apparatus according to claim 7 wherein said sensor isa surface resistivity sensor or a temperature detector or a scatteredlight detector.
 9. Apparatus according to claim 1 wherein said supplyapparatus further comprises a liquid source and said collected liquid isreturned to said liquid source thereby recycling the liquid.
 10. Anapparatus according to claim 1 further comprising a filter for filteringa collected liquid.
 11. An apparatus according to claim 1 furthercomprising a dosing tank for supplying concentrate to the liquid supplyapparatus to thereby regenerate said liquid.
 12. An apparatus accordingto claim 1 wherein said vehicle is an automobile.
 13. An apparatusaccording to claim 1 wherein said vehicle is an aircraft.
 14. Anapparatus according to claim 1 wherein said vehicle is a train.
 15. Amethod of maintaining a surface of a translucent screen of a vehiclehaving a plurality of edge regions comprising the steps of: detecting avehicle velocity and, responsive to said detected velocity, providing afirst edge region of said screen surface with liquid; causing the liquidto flow across the surface from the first edge region in the directionof a second edge region; and collecting said liquid in said second edgeregion; whereby said first edge region is selected from a top edgeregion and a bottom edge region, located below said top edge region, inresponse to said detected vehicle velocity.
 16. A method according toclaim 15 further comprising the steps of providing liquid to the firstregion under positive pressure; and collecting liquid from the secondregion under negative pressure.
 17. A method according to claim 15wherein said first region lies below said second region, said methodfurther comprising the steps of causing the liquid to flow upwards viaair flow.
 18. A method according to claim 15 wherein said second regionlies below said first region, said method further comprising the step ofcausing the liquid to flow downwards by gravity.
 19. A method accordingto claim 15 further comprising the steps of detecting a condition of thevehicle screen and outputting a condition control signal for controllingliquid supply to the screen.